Neighbor-joining tree of Pac WAK-like candidates and Arabidopsis RLK/Pelle subfamily Wak-like. Analysis was based on the aa sequences of: Pac (pac ♦) obtained with Wak-like primers; the complete Wak-like subfamily of Arabidopsis (◊), other sequences from plant species and one isotig extracted from a 454 transcriptome dataset of Pac, which has the typical Wak-like extracellular domains (black star) (Additional file 5). The Pac sequence containing the non-RD motif is evidenced by a dashed arrow and the motif is shaded black. The kinase domain region spanned subdomain II up to the beginning of IX. The brackets indicate a likely genetic correspondence between Pac and Arabidopsis clades (uncertain in the case of the dotted bracket). Residues next to the brackets of clade II are shared by all the members of clade II and of WAK1-headed clade of Arabidopsis and differentiate these sequences from all the other Arabidopsis and Pac WAK-like (−L) (see Additional file 9). See caption of Figure 1 for additional details on the representation of the tree.